This application seeks priority based on Patent Application No. 2007-35882, which was filed in Japan on Feb. 16, 2007. Accordingly, all of the content thereof is included in this application.
The present invention relates to a differential device provided with a pair of side gears and a pair of pinion gears housed inside a differential case, and specifically, to a countermeasure for providing lubricating oil smoothly to sliding sections with a pinion shaft supporting each pinion gear so as to be capable of sliding freely.
In vehicles such as automobiles, a rotation difference occurs between left and right drive wheels upon cornering, and therefore, a differential device has conventionally been provided in order to compensate for this rotation difference. As presented in JP 2004-90181A, for example, such a differential device includes a differential case, and a pair of side gears and a pair of pinion gears are housed therein. Furthermore, a pair of openings is formed in the differential case in order to insert the side gears and the pinion gears, and the side gears and the pinion gears having been inserted via the openings are supported inside the differential case. In specific terms, after each side gear is inserted via an opening and disposed in a desired location inside the differential case, each of the pinion gears is inserted and engaged with each side gear, and in this condition, the pinion shaft is passed through each of the pinion gears and fixed to the differential case.
However, when a rotation difference occurs between the left and right drive wheels upon cornering, each of the pinion gears slide around the axis of the pinion shaft. In such a case, the sliding surfaces of the pinion shaft with respect to each of the pinion gears are lubricated by lubricating oil having been stirred up by a final ring gear provided in the differential case. However, as the sliding surfaces of the pinion shaft with respect to each of the pinion gears are disposed inside the differential case, and in addition, the differential case itself is rotating, it is difficult to guide the lubricating oil having been stirred up by the final ring gear to the sliding surfaces of the pinion shaft with respect to each of the pinion gears, and the pinion gears slide thereupon in a substantially non-lubricated condition. For this reason, if a large rotation difference occurs between the left and right drive wheels, the sliding surfaces of the pinion shaft are liable to wear.
Accordingly, it is thought that a hollow channel can be formed inside a driveshaft, lubricating oil having been supplied from a casing housing the differential case can be guided to a central portion of an outer peripheral surface of the pinion shaft via the hollow channel in the driveshaft, and lubricating oil having been guided to the central portion of the outer peripheral surface of the pinion shaft can be fed to the sliding surfaces with respect to each of the pinion gears by a centrifugal force resulting from the rotation of the differential case.
However, in devices adopting the above approach, a strong sealing construction is required between a rotating body (that is, the driveshaft) and a fixed body (that is, the casing) upon guiding the lubricating oil from the casing to the hollow channel in the driveshaft, and the configuration thereof is extremely complicated.